SIGNIFICANCE and LONG-TERM OBJECTIVE: Chronic kidney disease (CKD), a progressive disorder that results in end stage renal disease (ESRD) requiring chronic hemodialysis or renal transplant, affects 400 million individuals globally and 26 million in the US. In ~50% of all cases CKD is caused by type 2 diabetes mellitus (T2DM). CKD and its comorbidities constitute a major financial burden to the health care system, warranting the development of new therapies to arrest or ameliorate the progression of the disease. Data obtained from this proposal are expected eventually to translate into clinical applications that will benefit those afflicted with CKD. RATIONALE and HYPOTHESES: We demonstrated that administration of allogeneic, bone marrow- derived mesenchymal stem cells (MSCs) to rats 1) affords renoprotection from Acute Kidney Injury (AKI), even with underlying CKD, and 2) prevents progression of CKD. This is achieved through MSC's anti- inflammatory and trophic anti-apoptotic, mitogenic and vasculoprotective actions. Results from our Phase I Clinical Trial, wherein at-risk cardiac surgery patients, the majority of whom had underlying CKD, were administered MSCs to prevent post-operative AKI, confirm those of preclinical studies, and indicate MSC administration is a safe, effective preventative therapy for AKI and both progression to CKD and of CKD itself. A Phase II Clinical Trial is currently enrolling study subjects. We hypothesize, therefore, that allogeneic MSC therapy effectively treats rats with CKD induced by 5/6th nephrectomy or T2DM (male Zucker, obese, rats), arresting or slowing the progression of CKD. Indeed, our preliminary work in the 5/6th nephrectomy CKD model in rats indicates that MSC administration given early or late post induction of CKD is effective, to variable degrees, in improving several manifestations of this form of CKD, i.e., systolic blood pressure, renal function, albuminuria and glomerular sclerosis. SPECIFIC AIMS: The present work is designed to fully investigate the therapeutic utility of adult stem cells for the treatment of CKD and underlying diabetes mellitus in rat models. Specifically, Aim 1. will test and develop optimal earl and late stem cell based intervention protocols in rats with CKD due to 5/6th nephrectomy or T2DM; Aim 2, will elucidate the mediator mechanisms that underlie the kidney protective effects of stem cells in rats with CKD caused by 5/6th nephrectomy or T2DM; and Aim 3 will assess whether the therapy found to be optimally effective in 5/6th Nephrectomy induced CKD (Specific Aim 1) is equally effective in CKD of diabetic Zucker rats. RESEARCH DESIGN and METHODS: Specific Aim 1 (SA): Using rat 5/6 nephrectomy CKD models, the optimal therapeutic efficacy of repeated and different intravenous cell doses, given early and/or late in the course of CKD will be determined by monitoring, over time or at study end, alterations in GFR, proteinuria, glomerulosclerosis, blood pressure, and other variables. SA 2: Mediator mechanisms that correlate with the therapeutic effects of MSCs that are documented in the studies of SA 1 are investigated, using as a guideline the anti-inflammatory, anti-fibrotic, anti-thrombotic and trophic actions of MSC that have been identified in AKI and other organ injuries. The importance of individual therapeutically effective factors expressed by MSCs will be further corroborated by knocking down their expression in MSCs (siRNA) or by blocking their identified mechanisms of actions. SA 3: It will be tested in male, obese, diabetic Zucker rats, whether MSC treatment improves blood sugar control per se and thereby the development of and/or progression of diabetic nephropathy.